Financing arrangements (Principal Amounts and Carrying Value of Long-term Borrowings) (Details) $ in Millions	Sep. 30, 2018 USD ($)	Sep. 30, 2018 EUR (€)	Sep. 30, 2018 CHF (SFr)	Sep. 30, 2018 GBP (£)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Unamortized discounts, premiums, issuance costs and fair value adjustments, net	$ (1,168)				$ (929)
Total carrying value of debt	34,427				35,342
Less current portion	(5,077)				(1,152)
Total long-term debt	29,350				34,190
Notes [Member] | 6.15% notes due 2018 (6.15% 2018 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 0				500
Interest rate, stated percentage	6.15%	6.15%	6.15%	6.15%
Notes [Member] | 4.375% €550 million notes due 2018 (4.375% 2018 euro Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 648				653
Face amount | €		€ 550,000,000
Interest rate, stated percentage	4.375%	4.375%	4.375%	4.375%
Notes [Member] | 5.70% notes due 2019 (5.70% 2019 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,000				1,000
Interest rate, stated percentage	5.70%	5.70%	5.70%	5.70%
Notes [Member] | 1.90% notes due 2019 (1.90% 2019 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 700				700
Interest rate, stated percentage	1.90%	1.90%	1.90%	1.90%
Notes [Member] | Floating Rate Notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 550				550
Notes [Member] | 2.20% notes due 2019 (2.20% 2019 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,400				1,400
Interest rate, stated percentage	2.20%	2.20%	2.20%	2.20%
Notes [Member] | 2.125% €675 million notes due 2019 (2.125% 2019 euro Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 783				810
Face amount | €		€ 675,000,000
Interest rate, stated percentage	2.125%	2.125%	2.125%	2.125%
Notes [Member] | 4.50% notes due 2020 (4.50% 2020 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 300				300
Interest rate, stated percentage	4.50%	4.50%	4.50%	4.50%
Notes [Member] | 2.125% notes due 2020 (2.125% 2020 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 750				750
Interest rate, stated percentage	2.125%	2.125%	2.125%	2.125%
Notes [Member] | Floating Rate Notes Due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 300				300
Notes [Member] | 2.20% notes due 2020 (2.20% 2020 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 700				700
Interest rate, stated percentage	2.20%	2.20%	2.20%	2.20%
Notes [Member] | 3.45% notes due 2020 (3.45% 2020 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 900				900
Interest rate, stated percentage	3.45%	3.45%	3.45%	3.45%
Notes [Member] | 4.10% notes due 2021 (4.10% 2021 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,000				1,000
Interest rate, stated percentage	4.10%	4.10%	4.10%	4.10%
Notes [Member] | 1.85% notes due 2021 (1.85% 2021 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 750				750
Interest rate, stated percentage	1.85%	1.85%	1.85%	1.85%
Notes [Member] | 3.875% notes due 2021 (3.875% 2021 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,750				1,750
Interest rate, stated percentage	3.875%	3.875%	3.875%	3.875%
Notes [Member] | 1.25% €1,250 million notes due 2022 (1.25% 2022 euro Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,451				1,501
Face amount | €		€ 1,250,000,000
Interest rate, stated percentage	1.25%	1.25%	1.25%	1.25%
Notes [Member] | 2.70% notes due 2022 (2.70% 2022 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 500				500
Interest rate, stated percentage	2.70%	2.70%	2.70%	2.70%
Notes [Member] | 2.65% notes due 2022 (2.65% 2022 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,500				1,500
Interest rate, stated percentage	2.65%	2.65%	2.65%	2.65%
Notes [Member] | 3.625% notes due 2022 (3.625% 2022 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 750				750
Interest rate, stated percentage	3.625%	3.625%	3.625%	3.625%
Notes [Member] | 0.41% CHF700 million bonds due 2023 (0.41% 2023 Swiss franc Bonds) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 713				719
Face amount | SFr			SFr 700,000,000
Interest rate, stated percentage	0.41%	0.41%	0.41%	0.41%
Notes [Member] | 2.25% notes due 2023 (2.25% 2023 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 750				750
Interest rate, stated percentage	2.25%	2.25%	2.25%	2.25%
Notes [Member] | 3.625% notes due 2024 (3.625% 2024 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,400				1,400
Interest rate, stated percentage	3.625%	3.625%	3.625%	3.625%
Notes [Member] | 3.125% notes due 2025 (3.125% 2025 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,000				1,000
Interest rate, stated percentage	3.125%	3.125%	3.125%	3.125%
Notes [Member] | 2.00% €750 million notes due 2026 (2.00% 2026 euro Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 870				901
Face amount | €		€ 750,000,000
Interest rate, stated percentage	2.00%	2.00%	2.00%	2.00%
Notes [Member] | 2.60% notes due 2026 (2.60% 2026 notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,250				1,250
Interest rate, stated percentage	2.60%	2.60%	2.60%	2.60%
Notes [Member] | 5.50% £475 million notes due 2026 (5.50% 2026 pound sterling Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 619				642
Face amount | £				£ 475,000,000
Interest rate, stated percentage	5.50%	5.50%	5.50%	5.50%
Notes [Member] | 3.20% notes due 2027 (3.20% 2027 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,000				1,000
Interest rate, stated percentage	3.20%	3.20%	3.20%	3.20%
Notes [Member] | 4.00% £700 million notes due 2029 (4.00% 2029 pound sterling Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 912				946
Face amount | £				£ 700,000,000
Interest rate, stated percentage	4.00%	4.00%	4.00%	4.00%
Notes [Member] | 6.375% notes due 2037 (6.375% 2037 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 552				552
Interest rate, stated percentage	6.375%	6.375%	6.375%	6.375%
Notes [Member] | 6.90% notes due 2038 (6.90% 2038 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 291				291
Interest rate, stated percentage	6.90%	6.90%	6.90%	6.90%
Notes [Member] | 6.40% notes due 2039 (6.40% 2039 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 466				466
Interest rate, stated percentage	6.40%	6.40%	6.40%	6.40%
Notes [Member] | 5.75% notes due 2040 (5.75% 2040 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 412				412
Interest rate, stated percentage	5.75%	5.75%	5.75%	5.75%
Notes [Member] | 4.95% notes due 2041 (4.95% 2041 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 600				600
Interest rate, stated percentage	4.95%	4.95%	4.95%	4.95%
Notes [Member] | 5.15% notes due 2041 (5.15% 2041 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 974				974
Interest rate, stated percentage	5.15%	5.15%	5.15%	5.15%
Notes [Member] | 5.65% notes due 2042 (5.65% 2042 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 487				487
Interest rate, stated percentage	5.65%	5.65%	5.65%	5.65%
Notes [Member] | 5.375% notes due 2043 (5.375% 2043 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 261				261
Interest rate, stated percentage	5.375%	5.375%	5.375%	5.375%
Notes [Member] | 4.40% notes due 2045 (4.40% 2045 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,250				2,250
Interest rate, stated percentage	4.40%	4.40%	4.40%	4.40%
Notes [Member] | 4.563% notes due 2048 (4.563% 2048 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,415				1,415
Interest rate, stated percentage	4.563%	4.563%	4.563%	4.563%
Notes [Member] | 4.663% notes due 2051 (4.663% 2051 Notes) [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 3,541				3,541
Interest rate, stated percentage	4.663%	4.663%	4.663%	4.663%
Notes [Member] | Other notes due 2097 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 100				$ 100